Fix: marshalJson error, when values contains map[interface{}]interface{} (#883)

Co-authored-by: tzz <tzz.wannamoney@qq.com>

config/reader.go

@@ -74,7 +74,7 @@ func (r *reader) Value(path string) (Value, bool) {
 }
 
 func (r *reader) Source() ([]byte, error) {
-	return marshalJSON(r.values)
+	return marshalJSON(convertMap(r.values))
 }
 
 func cloneMap(src map[string]interface{}) (map[string]interface{}, error) {